Technical Field
The present invention relates to a system and device for holding a bit for a tool so that the bit may be disassembled, re-assembled or cleaned when held. The invention also relates to a method of holding the bit using the holding device.
Background Information
A router is a tool, especially used in the woodworking industry, used for milling or hollowing out an area in the face of a work piece. Usually the material used in the fabrication of the work piece is wood or metal, but applying the router to other types of materials is also possible. There are several different types of routers. Nowadays, one of the more common types of router is a spindle router where a router bit is mounted onto a rotatable spindle that is rotatably engaged with an electric motor.
A typical router set-up includes a frame for supporting the router table. The router is mounted to the frame or table in such a way that the router bit will extend through an opening in the table. The work piece to be machined is supported by the table and is positioned so that the router bit will engage the work piece. Different bit sizes and shapes can be used, and the bit is easily exchangeable. The bit is engaged by a collet which is a part of the rotatable spindle that is connected to a motor drive on the router. The router collet and router bit mounted in the mouth of the collet are rotated by the motor drive round an axis perpendicular to the router table. Sometimes the position of the collet may be adjusted relative to the table, in a direction along the axis of rotation. In this case, the shape of the cut that is created by the bit is determined by the size and shape of the bit's cutter and the height of the bit relative to the upper surface of the router table.
One of the important variables determining the router's work is the shape of the router bit, particularly the configuration of the cutting surfaces and spacers that form the bit. A large variety of different router bits are available on the market, allowing an almost indefinite number of shapes to be routed into the work piece. One type of router bit is the so-called “stacked” router bit. Typically, a stacked router bit consists of a central shank which has a threaded top end onto which are mounted one or more removable bit elements. These bit elements include, but are not limited to, disc shaped cutters, ball bearings for guidance and/or various shims or spacers. To keep the stack of cutters and spacers firmly engaged on the shank, an end nut or similar device is tightened on top of the shank.
Adding or removing bit elements such as spacers or shims in between cutter elements modifies the thickness of wood removed in the routing process or the depth of cut in case of a ball bearing diameter change. The operator can select a variety of differently shaped cutters, or include various other types of bit element to change the overall profile routed into the work piece. In order to change the bit elements, it is necessary for the nut on the stacked router bit to be loosened and then the user may alter the number and type of bit element on the shank. Once the desired stack of bit elements is created, the nut is replaced on the end of the shank and is tightened. The shank is then engaged in the router collet and the router is activated.
The operation of disassembling and/or re-assembling stacked router bits while keeping the router bits chucked into the router is cumbersome for various reasons. First of all, unless the router itself is securely held, for instance in a base element such as a router table, it will tend to turn when the user applies torque to unscrew or refasten the end nut. While the router can be secured against turning, this tends to prevent the router table from being set up for alternative operations. Moreover, when the operation is performed in case the stacked router bit is clamped by the collet of the router, small parts, such as spacers, washers etc. may fall into the router motor housing. Furthermore, during the time interval wherein the router bit is chucked in the router collet for disassembling or re-assembling it, the router cannot be used for other purposes, such as milling another work piece. A further drawback is that the visibility is less than ideal, because the router collet generally cannot protrude far enough above the router table to allow a full and unencumbered view of the operation.
Alternatively, the stacked router bit could be held by a clamping element such as a hand plier or a steel bench vise. Generally, however, these clamping elements are less capable of resisting the considerable torque required to unscrew and re-fasten the end nut. Besides, these clamping elements will tend to engage directly on the router bit shank in such a manner that the risk is present to destroy the integrity of the bit's shank and to render it useless or even dangerous for further usage.
One device proposed in the prior art is that disclosed in a copending and allowed U.S. patent application to the present inventor, namely, U.S. patent application Ser. No. 12/393,340, the entire specification of which is incorporated herein by reference. This application describes the use of a holding device which includes a housing to be secured to a stationary base, such as the router table, and a clamping mechanism for releasably clamping the shank of the bit to the housing so that the bit may be disassembled, reassembled or simply held in a suitable position so that the cutter elements may be cleaned. In particular, the housing disclosed in this application defines a recess that is spaced from the peripheral edges of the housing. A movable element and stationary element are arranged inside the recess. The stationary gripping element includes a gripping area that is configured to engage the bit's shank. The movable element is rotated in a first direction within the recess to clamp the bit's shank in the gripping area. When the movable element is rotated in a second direction, the bit's shank is no longer clamped in the gripping area and is free to be withdrawn from the recess.
While the above holding device works well, there is still a need in the art for a device that is configured to engage a shank of a stacked router bit and tightly hold the shank against rotation during disassembly, reassembly or cleaning of the router bit.